Color-forming photographic compositions and processes



Patented Dec. 12,

UNITED STATES PATENT OFFICE COLOR-FORMING PHOTOGRAPHIC COM- POSITIONS AND PROCESSES No Drawing.

14 Claims..

This invention relates to photography. More particularly it relates to novel color-former components for use in photographic emulsions and developing processes and solutions. Still more particularly it relates to photographic elements bearing an emulsion layer which develops to form a dyed image and metallic silver in admixture therewith. The invention also pertains .to processes of producing colored images.

m This invention has for an object to provide new photographic color-former agents of improved spectral quality. A further object is to provide novel color-formers which couple readily upon development in colloidal emulsions to form water insoluble immobile dyes in situ with photographic images. A still further object is to' provide novel color-formers which will form dyes with the oxidation' products of aromatic amino developing agents or the corresponding nitroso compounds upon development of photographic images. A

still further object is to provide novel color formers which do not adversely affect the sensitivity of photographic emulsions, particularly gelatine silver halide emulsions. Still other objectswill 2 be apparent from a consideration of the herein-- after described invention."

It has been formerly taught to prepare colored photographs by, developing exposed silver salt emulsion layers in certain developing agents.

whose oxidation products are water-insoluble dyes. Thus, a silver halide layer, bearing a latent image, can be developed in an alkaline indoxyl. solution, whereupon a silver image is producedv Y alone with a blue dye image in situ with the silver. The silver image can be removed by Farmers reducer, revealing the dye image. In like manner, a photographic record can be developed in chlor-indoxyl to produce a green image and in thio-indoxyl for a red image.

It is also known, for the purpose of preparing color pictures, to develop exposed silver halide layers by agents whose oxidation products are not colored, but which will chemically unite or couple with other organic agents, called ,colorformers to form intensely colored dyes. These color-formers are not photographic developers,

are generally water-insoluble and produce dyes' in situ with, and simultaneously with the deposi- 'oxygen or sulfur.

Application November 23, 1938, Serial No. 242,112

(Cl. 95-6) I for example, thymol, benzoyl acetone, phenacyl chloride and paranitrobenzyl cyanide. I

These prior processes, however, have failed to produce colored images having the correct spectral qualities for color photography. Moreover, 5 these prior color-formers tend to have a harmful effect on the sensitivity of silver halid emulsions, so that, for these reasons, the color-formers already known have not provided a practical means for color photography. 10

The aboveand other objects may be accomplished, and the above-described disadvantages of prior art may be obviated by the following invention which comprises the use of the cyanacetamino-bis-azoles or color-formers in photographic l emulsions, solutions and processes. The color-, formers contemplated by this invention have the general formula: 1

nucleus, and X is an atom taken from the class consisting ofoxygen, sulfuryselenium and tellurium. -Thus, A may be a tetravalent benzene,

naphthalene, etc. nucleus in which the carbon atoms not. attached to X or N may have attached thereto H, alkyl', e. g., methyl, ethyl, propyl, etc.;

- aryl, e. g., phenyl, tolyl, naphthyl'; alkoxy, e. g.,

methoxy,- ethoxy; halogen, e. g., chlorine, bromiiie; sulfonic or carboxylic acid groups.

In' a preferred embodiment of the invention, A is a tetravalent 1, 2, 4, 5-benzene radical and X is,

These compounds have the following general formulae:

wherein X is oxygennrs'ulfur and R and Rmay be hydrogen, allcyi, aryl, alkoxy, halogen, suifonic or carboxylic acid groups.

The invention will be further illustrated but I is not intended to be limited by the following examples in which the parts stated are parts The di-cyanacet derivative of 2,6-diamino-p-pbenzobisthiazole is prepared as follows. Ethyl cyanoacetate (10 parts) is heated to 150 in an open vessel and 2.5 parts of 2,6-diamino-p-p-benzobisthiazole are added in small portions. The temperature is maintained at 160-170 for hour, and after cooling, the pale yellow product is filtered and washed with ether. The compound has a melting point above 270 C., is but slightly soluble in alcohol, readily soluble in glacial acetic acid, dimethyl formamide, and aqueous caustic alkali.

The 2,6-diamino-p-/3-benzobisthiazole can be prepared by reacting p-phenylene diamine hydrochloride and ammonium thiocyanate and reacting the resulting p-phenylene-bis-thiourea with bromine in a dry chlorobenzene medium and heating the resulting product. The isomers and analogous compounds used as starting materials may be prepared in a similar manner.

In place of the 2,6-diamino-p-p-benzo bisthiazole of this example the same amount of the corresponding meta compound may be used. Likewise the corresponding substituted derivatives, that is, those in which at least one hydrogen atom of the benzene nucleus is substituted by an alkyl, aryl, alkoxy, halogen, sulfonic acid or carboxylic acidgroup may be used to form the corresponding cyanaeetamino-bis-azoles. In addition to afore-specified compounds the diamino-bis-azoles' of the following general formulae may be used:

wherein R and R have the above significance, may be used for condensation with ethyl cyanacetate. Similarly; the corresponding oxazoles may be se V EXAMPLE II A developer solution containing the following ingredients was prepared: Diethyl-p-phenylenediamine,

hydrochloride "grams" 2 Sodium sulfite, anhydrous do 5 Sodium carbonate, anhydrous do 20 Water to liter 1 To which is added-- Dicyanacetamino-1,2,4,5-p-benzobis-thiazole gram 1.0 Ethyl alcohol cubic centimeters 100 A photographic element containing an exposed silver salt image was developed in the above,

solution and a bluish-red and magenta dyed image of good tinctorial strength was obtained.

Similar results were obtained by the use of the following compositions:

To 100 cos. of a developer having the following composition: Diethyl-p-phenylenediamine hydrochloride --grams-.. 2 Sodium sulfite (anhydrous) do 5 Sodium carbonate (anhydrous) do 20 Water cubic centimeters 1000 are added from 0.1 to 1.0 gram of diacyanacetamino-1,2,4,5-m-benzo-bis-thiazole dissolved in a few ccs. of ethyl alcohol. An exposed photographic element containing exposed silver salts is then developed in aforedescribed solution.

A positive silver image which has been bleached to a silver salt image may be redeveloped in this solution. A suitable bleach may comprise a liter of water containing about 35 grams of potassium ferricyanide and 5 cos. of 20% ammonia water.

' Thorough washing between treatments is essential. After color-development, the silver may be removed, leaving a pure dye image, by bleaching in ferricyanide, for example, and fixing in plain hypo.

In place of the dialkyl-substituted p-phenylenediamines set forth in the preceding examples may be substituted various other aromatic amino developing agents which have at least one unsubstituted amino group. Thus, the monoalkyl arylene diamines, such as N-ethylamino aniline, N-methylamino aniline, N-propylamino aniline; 14-naphthylene diamine, l-N-diethyl naphthylamine-1, phenylene diamine as well as the salts of these bases may be used. Thus, the aromatic rings may be substituted with non-reactive groups, e. g., alkyl, aryl, ester, alkoxy and halogen groups. The salts of the bases such as the hydrochloride and sulfate are generally used because ofv their stability. The corresponding nitroso compounds may also be used.

The color-formers hereof are not limited in their use to developer solutions. In fact, they the invention.

EXAMPLE VI .are preferably used in photographic emulsions. The following example illustrates this feature of oughly mixed. This color forming solution is then added to a liter of a silver-bromide gelatine emulsion. The emulsion is then coated upon a suitable photographic support such as paper or a cellulose derivative base, or upon another photographic emulsion which may or may not contain a different color forming dye component. After exposure in a camera or by printing through appropriate color records the photographic element may be color developed with a developing solution containing p-aminodiethylaniline to form a dyed image.

In place of the specific cyanacetamino bisazole of this example may be substituted any of the herein described compounds of that type. Furthermore, any of the herein disclosed developing agents may be used with the latter azoles.

While it is preferred 'to employ silver halidegelatin emulsions, other emulsions comprising other binding agents may be used. As examples of suitableemulsions, mention is made of collodion, gum arabic, starch and albumin emulsions, and bichromated colloid emulsions. The silver halide emulsions may contain the usual sensitizers such as the cyanine, carbocyanine, pseudo cyanine, cyazine, carbocyazine, etc. salts or bases which are used to extend the sensitivity of the photographic emulsions.

In the form of color-forming developers, the above-described compounds may alsobe used to re-develop bleached silver images. Thus, a silver image may be bleached in potassium ferro-.

cyanide or a mixture of chromic and hydrobromic acids and re-exposed, whereupon the bleached image can be re-developed to silver and a dye image by the color-forming developers above described. After development, the silver is removed by any of the well known reducers such as Farmer's reducer.

Among the advantages of this invention is the fact that the colors produced are less strongly blue-absorbing than the old art. compounds, which is necessary for 3-color photography, and less strongly red absorbing which is also necessary. The colors still retain the necessary high absorption of green. A further advantage resides in the fact that the resulting dyes do not migrate in emulsion layers. The color-formers are furthermore somewhat immobile.

The fact that the dye images produced according to this invention are magenta is rather surprising since a consideration of their chemical structure would lead one to suspect that they would be yellow-to-orange color formers. Thus, a new class of color formers which are distinctly diiIerent from the methyphenyl pyrazolones and have advantages thereover, is provided.

application is a continuation-in-part of applicants co-pending application, Serial No.

126,735, filed February 19, 1937, now Patent N0.

2,140,540, issued December 20, 1938.

As many apparently widely difierent embodiments of this invention may be made without departing from the spirit and scope thereof, it

is to: be understood that we do not limit ourselves to the specific embodiments hereof except as defined by the appended claims.

We claim:

1. A color-forming photographic developer .comprising an aromatic amino photographic developing agent and a dicyanacetamino biscomprising an aromatic amino photographic developing agent and a dicyanacetamino bisthiazole.

5. A color-forming photographic developer comprising an arylene diamino photographic developing agent and a dicyanacetamino-benzobis-thiaz'ole. a

6. A color-forming photographic layer comprising-a light sensitive silver halide emulsion containing a dicyanoacetamino-benzo-bis-azole.

7. A photographic element bearing a light sensitive silver halide emulsion containing a dicyanoacetamino benzo-bis-thiazole.

8. A photographic element bearing a colorforming light sensitive silver halide emulsion containing dicyanacetamino-1,2,4,5-m-benzo-bisthiazole.

9. A photographic element bearing a colorforming light sensitive silver halide emulsion containing dicyanacetamino-1,2,4,5-p-pbenzobis-thiazole.

10. A process which comprises developing a photographic element bearing an emulsion containing a light sensitive material in the presence of a dicyanacetamino-aro-bis-azole.

11. A process which comprises developing a A photographic element bearing an emulsion layer containing a light sensitive silver halide with an arylene diamino photographic developing agent in the presence of a dicyanacetamino-benzo-bisthiazole.

12. As newcompoun'ds the dicyanacetaminoaro-bis-azoles.

13. As new compounds the dicyanacetaminobenzo-bis-azoles.

14. As new compoundsthe dicyanacetamino- I benzo-bis-thiazoles.

- EDMUND B, MIDDLETON.

ANDREW B. JENNINGS. 

